Mine roof supports



A ril 7, 1964 J. COOKE MINE ROOF SUPPORTS 3 Sheets-Sheet 1 Filed May 2, 1961 INVENTOR:

1014K COOK-E3 April 7, 1964 J. COOKE MINE ROOF SUPPORTS 3 Sheets-Sheet 2 Filed May 2, 1961 INVENTOR:

J'OH N C ooKE April 7, 1964 .1. cooKE MINE ROOF SUPPORTS 3 Sheets-Sheet 3 Filed May 2, 1961 m ml J'OH N COO/(E INVENTOR:

United States Patent ()fiice 3,127,748 Patented Apr. 7, 1964 3,127,748 MINE RUG SUFPORTS John Cooke, Walkden, England, assignor to Gullick Limited, Wigan, Engiand, a British company Filed May 2, 1%1, Ser. No. 107,195 Claims priority, application Great Britain May 10, 1960 3 Claims. (Cl. 61-45) This invention is for improvements in or relating to mine roof supports of the kind comprising an hydraulic or other pressure-fiuid-operated prop or series of props and a pivoted or articulated extension bar generally in the form of a cantilever. Such roof supports are used in the well known longwall method of mining, the cantilever extension bar projecting forwardly of the main roof supporting prop or chock and serving to provide roof support over, for example, a conveyor. By pivoting or articulating the extension bar it can be set at an angle, to the main bar or member supported by the prop or chock, to allow for irregularities in the roof.

It is necessary that the means supporting the cantilever extension bar against the roof should be such that the bar can give to a controlled extent to relieve it of excessive loading as may occur, for example, when a roof is settling down. Conveniently this is effected by a pressure-fluid or hydraulic control arrangement.

An object of the present invention is to provide an improved control arrangement for the extension bar.

According to the present invention there is provided a pressure-fluid-operated mine roof support in which a prop, adapted to be extended by fluid pressure to secure the support between floor and roof, includes a member adapted to act on a pivoted or articulated extension bar so as to apply said bar to the roof, the pressure fluid systern of the support including a bleed valve or the like adapted to bleed-off pressure fluid when the support is subjected "to excessive loading.

According to a further feature of the invention there is provided a pressure-fluid mine roof support having a cantilever extension bar or member arranged so that when subjected to excessive pressure it will, in relieving itself of such excessive pressure, increase the fluid pressure acting to hold the main support against the roof. It has been found that excessive loading on the cantilever extension bar is often due to weakness on the part of the main support. The arrangement just described automatically cures this weakness.

According to a further feature of the present invention there is provided a mine roof support comprising a roof bar, pressure fluid prop means for supporting said roof bar, a roof bar extension pivoted or articulated to said roof bar and an auxiliary ram in said prop means acting on said roof bar extension, when the prop means is extended, to apply said roof bar extension to the roof, the pressure fluid system of the support including a bleed valve or the like adapted to bleed-01f pressure fluid if the support, including the roof bar extension, is subjected to excessive loading.

One particular embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing. In the drawing:

FIGURE 1 is a side elevation partly in section of a complete roof supporting chock.

FIGURE 2 is a detail sectional view showing more particularly the roof bar extension supporting and control means,

FIGURE 3 is a further sectional side elevation, the actual construction of the chock being slightly different in some respects from that shown in FIGURE 1, and

FIGURE 4 is a diagram of the hydraulic circuit.

The chock shown on the drawing comprises a base or floor member 1 on which there is mounted a front prop or leg 3 and a rear prop or leg 4. The arrangement about to be described can, however, be applied to a chock having more than two legs. Furthermore, two of the twoleg units shown on the drawing may be combined to form a four-leg unit or chock.

Mounted on the two props 3 and 4 is a roof bar 5 which has a cantilever roof bar extension 6.

Located within the base or floor member 1 is a doubleacting hydraulic ram 2 which is coupled to the conveyor C. The arrangement is such that as cutting of the coal proceeds the ram 2 can be operated to push over the conveyor using the roof support as an abutment prop. When the conveyor has been pushed over, the roof support is lowered by discharging fluid from the legs or props 3 and 4 and the ram 2 is then operated in the reverse direction so that, using the conveyor as an anchorage, the roof support is drawn forwardly. After this has been effected the legs are, of course, again extended so as to apply the bar 5 and the extension bar 6 to the roof. The manner in which the extension bar 6 is applied will be described more fully hereafter. The supply and discharge of hydraulic pressure to the roof support is controlled by a valve indicated diagrammatically at 10 through pipe P, the bore 20 of bolt 21 and passageway 22 in piston head 7a, FIG. 3.

The roof bar 5 is of rectangular hollow construction and is formed internally with a pivot 14 for the cantilever extension 6. Trunnions or laterally projecting studs may be provided at 17 which engage in slots in the side walls of the roof bar 5 to provide non-load taking locations.

The item 14 is, in fact, a pivot for the inner end of the bar 6 which is somewhat like a knife-edge pivot but with a rounded instead of a sharp edge. The inner end of the bar 6 rests against and pivots on this pivot 14. The item 17 is a pin which projects through and extends laterally on either side of the bar 6, trunnion fashion, and is adopted to move up and down in arcuate slots (not shown) in the side members or webs of the roofing bar 5. If it were not for this arrangement the inner end of the bar 6 could slide off the pivot 14. As the cantilever bar 6 pivots on the pivot 14, the trunnions 17 move up and down in the arcuate slots above referred to.

For the purpose of the present invention the front leg 3 of the prop consists of an outer tube 3a, an inner member or piston 7 which is of tubular form, a top cap 11 and a separate or auxiliary piston 8 which Works in the tubular inner member or piston 7 and is provided with a sealing leather 9. Shouldered rod 18 is fixed to piston 8 and extends upwardly through an opening in cap 11 into engagement with the underside of extension bar 6. The bottom end of the tubular piston 7, which forms a cylinder for the auxiliary piston 8 has a piston head 7a fitted with a cup leather 7b and which works in the outer tubular member 3a of the prop.

The front and rear legs 3 and 4 are coupled together hydraulicaliy, as indicated in FIGURE 4, and have a common spring-loaded and adjustable bleed valve 10a which sets the yield load of the unit. The arrangement may be modified to include an isolating valve between legs 3 and 4.

The load on the main roof bar 5 is transmitted onto the front leg 3 through a socket 12 at the annular line 13. A similar arrangement may be provided for the rear leg 4, as shown in FIGURE 3, or the load may be transmitted directly onto the rear leg as shown in FIG- URE 1. Flexible collars may be provided at 15 and 16 (see FIGURE 1).

The roof load carried by the extension bar 6 is transmitted to the plunger or piston 8 by connecting rod 18 and is held by the fluid pressure acting on the cup leather seal 9. The rear of the extension bar pivots on the block 14.

For a given leg or prop size and load-carrying capacity, the tip loading of the extension bar 6 is controlled by the size of the bore of the tubular member 7 and the distance from the centre of the piston 8 to the pivot 14.

When hydraulic pressure is applied to raise the props 3 and 4 to support the roof, the pressure in the prop 3 also raises the piston 8. This applies the roof bar extension 6 to the roof but in such a manner as to conform to the roof formation. Any excessive load on the extension bar 6 depresses the piston 8 and fluid is released from the main bleed or pressure relief valve at the set pressure.

Excessive load on the extension bar 6 is usually caused by too low a resistance of the unit proper to the roof. The downward movement of the extension bar under excessive load generates a higher pressure in the front leg and hence also in the back leg. This increases the resistance of the unit proper to the roof and removes the cause of the excessive loading on the extension bar.

In some circumstances the front and rear legs, particularly of a four-leg unit, can be on separate circuits. Each circuit is preferably provided with its own bleed valve. In this case the cantilever bar will usually be arranged to act only on the front leg or legs.

It will be appreciated that from one aspect the present invention, broadly speaking, is based on the principle of a cantilever bar sensing roof movement ahead of the chock proper and adjusting the pressure or inducting a higher pressure as required in the chock leg or legs. A bleed valve or valves may or may not be associated with such an arrangement. Furthermore, the cantilever bar may act to transfer pressure fluid from one prop or leg to another or others as above described or it may act on a separate piston and cylinder device connected to the circuit of the main chock so that at appropriate times pressure fluid is forced from a separate cylinder to a leg or legs of the main chock.

Arrangements according to the present invention are, as previously indicated, particularly applicable to coal extraction by the long wall method of working. In one such method a Panzer conveyor runs behind the coal face, a coal cutter runs on the conveyor and cuts a web of coal from the face and behind the conveyor there is a walkway to allow access for personnel and behind this walkway self-advancing supports to control the mine roof and move over the conveyor. Coverage over the walkway and conveyor is provided by the cantilever bars associated with the self-advancing supports. For several reasons, under certain conditions, after re-setting the supports, a certain amount of convergence takes place before full load is taken by the support. The reasons for this include:

(a) Compression of loose material between the supports and the roof and floor.

(b) Expansion of the conduits and hydraulic units under increasing pressure.

(a) Hydraulic fluid compression.

This convergence can cause disruption of the roof between the support and the coal face. A support set against the conveyor can improve matters but is more expensive and causes some obstruction. An arrangement according to the present invention provides at least a substantial solution to these problems.

I claim:

1. A hydraulically-operated mine roof support comprising a base, a roof support member, an extensible leg having a tubular ram movably supporting said roof support member from said base, a pressure fluid system in which said leg is connected at a level below said ram whereby the ram can be moved upwardly with respect to the leg to lift the roof supporting member to secure the support between floor and roof of a mine, a passageway through said tubular ram at the lower part thereof communicating said pressure fluid system with the interior of said tubular ram, a cantilever bar sensitive to roof movement articulated to the roof support member at a point above and inwardly of the point of support of said leg and extending outwardly from the support member to bear against a mine roof, an auxiliary fluid pressure ram in said leg operative to act on said cantilever bar and apply it to the roof, said auxiliary ram being coaxial with and having its piston working in the tubular ram of said leg, and a rod connected to the piston of said auxiliary ram and extending through the top of said tubular ram into engagement with said cantilever bar at a point spaced outwardly from its point of articulation to the roof support member.

2. A support as claimed in claim 1 and having in the pressure-fluid system a pressure responsive bleed-valve for bleeding-off pressure-fluid from the system when the pressure therein exceeds a predetermined limit.

3. A support as claimed in claim 1 wherein said roof support member has spaced upper and lower walls, said cantilever bar being articulated to the roof support member at a point between the upper and lower walls, an opening in said lower Wall, a flanged socket on the upper end of said tubular ram protrudinginto said opening with its flange engaging the underside of said lower wall to support the roof support member from said tubular ram, and said rod connected to the auxiliary ram passing through said socket into engagement With the cantilever bar.

References Cited in the file of this patent FOREIGN PATENTS 1,180,955 France Jan. 5, 1959 (Corresponding British Patent 856,720, Dec. 21, 1960) 

1. A HYDRAULICALLY-OPERATED MINE ROOF SUPPORT COMPRISING A BASE, A ROOF SUPPORT MEMBER, AN EXTENSIBLE LEG HAVING A TUBULAR RAM MOVABLY SUPPORTING SAID ROOF SUPPORT MEMBER FROM SAID BASE, A PRESSURE FLUID SYSTEM IN WHICH SAID LEG IS CONNECTED AT A LEVEL BELOW SAID RAM WHEREBY THE RAM CAN BE MOVED UPWARDLY WITH RESPECT TO THE LEG TO LIFT THE ROOF SUPPORTING MEMBER TO SECURE THE SUPPORT BETWEEN FLOOR AND ROOF OF A MINE, A PASSAGEWAY THROUGH SAID TUBULAR RAM AT THE LOWER PART THEREOF COMMUNICATING SAID PRESSURE FLUID SYSTEM WITH THE INTERIOR OF SAID TUBULAR RAM, A CANTILEVER BAR SENSITIVE TO ROOF MOVEMENT ARTICULATED TO THE ROOF SUPPORT MEMBER AT A POINT ABOVE AND INWARDLY OF THE POINT OF SUPPORT OF SAID LEG AND EXTENDING OUTWARDLY FROM THE SUPPORT MEMBER TO BEAR AGAINST A MINE ROOF, AN AUXILIARY FLUID PRESSURE RAM IN SAID LEG OPERATIVE TO ACT ON SAID CANTILIVER BAR AND APPLY IT TO THE ROOF, SAID AUXILIARY RAM BEING COAXIAL WITH AND HAVING ITS PISTON WORKING IN THE TUBULAR RAM OF SAID LEG, AND A ROD CONNECTED TO THE PISTON OF SAID AUXILIARY RAM AND EXTENDING THROUGH THE TOP OF SAID TUBULAR RAM INTO ENGAGEMENT WITH SAID CANTILEVER BAR AT A POINT SPACED OUTWARDLY FROM ITS POINT OF ARTICULATION TO THE ROOF SUPPORT MEMBER. 